On the role of grain growth, recrystallization and polygonization in a continuum theory for anisotropic ice sheets
On the role of grain growth, recrystallization and polygonization in a continuum theory for anisotropic ice sheets
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关于晶粒生长、再结晶和多边形化在各向异性冰盖连续介质理论中的作用
DOI：
10.3189/172756404781814410
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发表时间：
2004
影响因子：
2.9
通讯作者：
K. Hutter
中科院分区：
文献类型：
--
作者：
L. Placidi;S. H. Faria;K. Hutter
摘要我们概述了如何将多晶冰的微尺度效应结合到一个连续描述中。实际上，对南极冰芯的分析表明，不同的微结构通常会产生不同的响应，即c轴的不均匀分布导致了各向异性行为。人们已经认识到，为了描述某些微观结构过程，如再结晶或多边形化，我们需要一个能够开启它们的参数(例如，位错密度或与之相关的晶格扭曲能)。考虑到这一点，最近提出了各向异性冰盖重结晶的连续统理论的平衡方程。在这项工作中，我们检查了一些本构变量的关系，以考虑晶界迁移、形核和多边形化的影响。我们通过与伯德(南极洲)冰核的前1200米进行明确的比较来检验我们的假设。现有文献通常给出正常晶界长大与晶界迁移速率之间的关系。文中提出了一个考虑了多边形化影响的正常晶粒长大方程。它是基于南极洲同一岩心的实验数据。多角化是一个微观过程，但在这里，我们用连续多样性混合物理论来描述促进微晶碎裂的弯曲应力。
Abstract We outline how to incorporate microscale effects of polycrystalline ice into a continuum description. Actually, analyses of ice cores in Antarctica show that different microstructures generally produce different responses, i.e. a non-uniform distribution of c axes gives rise to anisotropic behaviour. It has been recognized that, to describe certain microstructural processes, like recrystallization or polygonization, we need a parameter able to switch them on (e.g. dislocation density or its associated lattice distortion energy). With this in mind, balance equations for a continuum theory of an anisotropic ice sheet undergoing recrystallization have been recently proposed. In this work, we examine relations for some constitutive quantities, in order to take into account the effects of grain-boundary migration, nucleation and polygonization. We check our assumptions by explicit comparison with the first 1200 m of the Byrd (Antarctica) ice core. Current literature usually gives a relation between normal grain growth and grain boundary migration rate. Here, an equation for normal grain growth which also incorporates the influence of polygonization is suggested. It is based on experimental data from the same core in Antarctica. Polygonization is a microscopic process, but here we present a continuum description of the bending stresses which promote the fragmentation of crystallites in terms of the theory of mixtures with continuous diversity.